The present invention relates to a conductive implantable lead and, more particularly, to a neural stimulator lead which may be installed and fixed in the epidural space of the spinal cord of a patient.
Neural stimulator electrodes and leads have been employed in the past which have been implanted in the epidural space of the spinal cord of a patient for stimulating selected locations along the spinal cord for such purposes as the relief of pain. One such lead is disclosed in U.S. Pat. No. 4,285,347 in which the leading distal end of the lead is axially moved along the epidural space in the spinal cord by passing the end through a Tuohy needle and pushing the end of the lead to the location on the dura where it is to stimulate the spinal cord. That lead has a configuration at its distal end and adjacent the stimulating electrode which may be deformed during installation of the lead by a stylet which passes through the lead to ease its introduction. Once the lead has been positioned as desired, the stylet is removed to cause the distal end of the lead to expand to minimize subsequent axial or lateral movement of the lead once it has been placed. In the lead disclosed in that patent, the leading distal end of the lead is inaccessibly located in the epidural space at all times during introduction and fixation and, thereby, is capable of being manipulated from only one end thereof.
Implantable leads incorporating the principles of the present invention enjoy several advantages over the prior neural stimulator leads. Implantable leads incorporating the principles of the present invention greatly facilitate the initial positioning of the lead electrodes with a minimum of effort and a minimum of trauma to the patient and essentially preclude the need for repositioning of the lead once it has been positioned. Implantable leads incorporating the principles of the present invention enable fixation of the lead at two points, thus minimizing the possibility of axial or lateral movement of the lead once it has been installed. Implantable leads incorporating the principles of the present invention may also eliminate the need for the use of a stylet during installation, thereby minimizing pain and trauma to the patient which might be associated with the installation and fixation procedure. Implantable leads incorporating the principles of the present invention enable precise control of the lead during installation and fixation by providing for manipulation simultaneously of both ends of the lead. Implantable leads incorporating the principles of the present invention may also include projections which stabilize the lead against accidental displacement once it has been properly placed at the location which is to be stimulated.
In one principal aspect of the present invention, an elongate, flexible, electrically conductive stimulator lead for implantation in the body of a patient includes an electrical conductor, a non-conductive coating covering the conductor and an electrode connected at one end of the conductor with at least a portion of the electrode being in electrical communication with the exterior of the coating to define an electrical contact region. The improvement in the lead comprises the contact region being located substantially intermediate the distal ends of said lead such that a substantial portion of the length of the lead extends in both directions from the electrode.
In another principal aspect of the present invention, the conductor of the aforementioned lead extends from the intermediately located electrode to a location adjacent one distal end of the lead.
In still another principal aspect of the present invention, the coating of the first mentioned lead comprises a tube having a lumen therein, a portion of the lumen containing the conductor, and an opening defined in the other distal end of the lead.
In still another principal aspect of the present invention, the coating of the first mentioned lead includes at least one flexible projection extending from the exterior of the coating adjacent the contact region for fixing the lead against displacement.
In still another principal aspect of the present invention, in the last mentioned lead the flexible projection comprises an elongate wing extending laterally from the coating and the length of the wing is approximately twice the diameter of the lead.
In yet another principal aspect of the present invention, the aforementioned leads are neural stimulator leads for stimulating the spinal cord of a patient, and the leads are sized for installation and fixation in the epidural space of the patient.
In still another principal aspect of the present invention, a combination for the introduction of a stimulator lead in the body of a patient comprises an electrically conductive stimulator lead, including a non-conductive coating and a conductor covered thereby, and an electrode in the stimulator lead in electrical communication with the exterior of the coating to define an electrical contact region. A second elongate flexible lead is provided and coupling means is provided for coupling at least one distal end of the stimulator lead with an end of the second lead to enable the stimulator lead to be pulled into a position in the patient's body where stimulation is to be effected.
In still another principal aspect of the present invention, the electrode as previously described is located substantially intermediate the distal ends of the stimulator lead and the conductor extends from the electrode to adjacent one distal end of the stimulator lead. The aforementioned coupling means is located adjacent the other distal end of the stimulator lead.
In still another principal aspect of the present invention, the aforementioned second lead includes groove means, such as bulbous means, at one end thereof to assist in snaring the end.
In still another principal aspect of the present invention, the last mentioned combination also includes snare means for tightening about the groove means and the snare means may comprise a movable loop.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.